comp.lang.idl-pvwave archive: archive » Re: How do I prevent underflow errors?

Home » Public Forums » archive » Re: How do I prevent underflow errors?

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: How do I prevent underflow errors? [message #14357 is a reply to message #14351]

Wed, 17 February 1999 00:00

Ethan Alpert
Messages: 2
Registered: February 1999

Junior Member

Phillip & Suzanne David wrote:

> I have a large array of data that I'd like to plot with the contour routine.
> However, the dynamic range of the data is very large, with values as large as
> 1e36 and as small as 1e-40. I noticed that contour accepts float data, not
> double data. This data is outside the range of float data, so it needs to be
> scaled for the contour routine. I don't really care to differentiate the
> 1e-40 from 0, but would like to be able to handle values up to the 1e36. I
> was going to scale the data by the largest value (i.e.,
> PlotData=Float(Data/Max(Abs(Data)))). This puts the data in the range of -1.0
> to 1.0. This should be fine for Contour, but I get an underflow error when
> converting from double data to float data. I understand that the data will
> come out with a 0 instead of 1e-76, and don't really care. How do I get IDL
> to ignore the underflow and just convert the value?

Is your data all possitive? Have you considered contouring the log of the data?
The contours generated by taking the log of the data will be the same if
you set the contour intervals correctly.

This should solve the problem.

-ethan alpert

>
> Phillip

--
------------------------------------------------------------ -------------------
Ethan Alpert ethan@ncar.ucar.edu
------------------------------------------------------------ -------------------

Report message to a moderator

[Message index]

		Re: How do I prevent underflow errors? By: Ethan Alpert on Fri, 19 February 1999 00:00
		Re: How do I prevent underflow errors? By: meron on Thu, 18 February 1999 00:00
		Re: How do I prevent underflow errors? By: thompson on Thu, 18 February 1999 00:00
		Re: How do I prevent underflow errors? By: Phillip & Suzanne on Wed, 17 February 1999 00:00
		Re: How do I prevent underflow errors? By: meron on Wed, 17 February 1999 00:00
		Re: How do I prevent underflow errors? By: Ethan Alpert on Wed, 17 February 1999 00:00
		Re: How do I prevent underflow errors? By: Michael Viskum on Wed, 17 February 1999 00:00
		Re: How do I prevent underflow errors? By: Craig Markwardt on Wed, 17 February 1999 00:00
		Re: How do I prevent underflow errors? By: davidf on Tue, 16 February 1999 00:00

Previous Topic:	Re: Byte to Real conversion
Next Topic:	IDL and Image Segmentation

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 15:17:27 PDT 2025

Total time taken to generate the page: 0.87759 seconds